Four-masted 'Alastor' - what kind of vessel

Hello there,
I'm just about to finish the series (just started 'Blue at the Mizzen'), but there is a question I've got concerning "The Wine-Dark Sea". As you surely remember Jack fights and defeats a french pirate ship, the four-masted Alastor. What kind of vessel is this supposed to be? I cannot find any reference to four-masted ships at that time.

Thanks a lot

The earliest reference I can find to a four master is the L'invention of 1801 so they existed but what type Jack met I don't know

That's really fascinating! The l'Invention seems to have been designed and built by its commander Thibaut as a privateer (!). Just 8 days after its launch it was captured by the frigate Immortalité. It was sold and re-rigged as a three-masted ship.

Great info - thanks a lot.